The present invention relates generally to the field of water-borne vehicles, and is more particularly concerned with boat structures of the portable knockdown type.
Heretofore, knockdown boats and boats with inflatable hulls have not been compatible with the shape required to provide a boat structure capable of high performance, as for example, in a catamaran, which requires a long and narrow configuration. Experiments have indicated that even the use of high inflation pressures of the order of two to three pounds per square inch for a conventional envelope structure does not produce the desired results, and requires expensive fabrication techniques.
In the present invention it has been found that the above difficulties can be overcome by utilizing an inflatable low pressure envelope that can be readily conformed to the required shape for high performance operation. The necessary rigidity may be obtained through the use of light weight, high-tempered aluminum tubing members which are held within a fabric surface sleeve of the envelope and extend between its ends. The tubing members are longitudinally curved to conform to the tapered ends of the envelope so that, when the envelope is inflated, the tubing members will be automatically retained in a proper position.
In the catamaran embodiment, the two hulls formed by the inflated envelopes are bridgingly retained in operative positions on the opposite sides of a central elongate frame member of fiberglass by means of forward, mid and aft tubular bridging frames having their outer ends connected to the hull envelopes.
Each envelope preferably has a fore and aft tubular rigidifying member, and these tubular members are arranged so that they will have their adjacent ends in abutting relation at approximately the mid-length of the envelope. The forward tubular members are laterally extended at the forward ends of the envelopes in a direction towards each other, and connected to the forward end of the central elongate frame member to provide a rigid frame structure. The mast and rudder are carried by the central frame member.
By utilizing the features of construction according to the present invention, a practical catamaran embodiment would have an approximate length of 15', a beam of 5'2", sail area of 100 sq. ft., maximum hull diameter of 15", provide for a crew weight of 275 lbs., and have a total assembled weight of approximately 55 lbs. In its knockdown condition, the boat collapses into a portable package of approximately 12.5' .times. 2.5'.